Method and apparatus for digitally evaluating insertion quality of customized orthodontic arch wire

ABSTRACT

A method and apparatus is provided for digitally checking the insertion quality of a target customized virtual arch wire designed during treatment planning prior to actually manufacturing the target arch wire. The method includes the steps of digitally simulating the insertion of the customized target virtual arch wire into the virtual brackets placed up on virtual teeth of a patient in an initial state of interest for checking if the arch wire could be inserted into the virtual brackets without conflicts or collisions. The initial state may be a malocclusion state or any intermediate treatment state of the patient. In the event the target virtual arch wire would cause conflicts, then the simulation optimizes the arch wire design in an attempt to eliminate the conflicts. In another aspect, a method is provided for selecting the recommended starting point for inserting the customized arch wire in the brackets placed on the dentition of the patient in the initial state.

BACKGROUND OF THE INVENTION

A. Field of the Invention

This invention relates to the field of computerized techniques fororthodontic treatment planning for human patients. More particularly,the invention is directed to a method and apparatus for checking if atarget virtual orthodontic arch wire can be inserted into virtualbrackets placed on the virtual malocclusion dentition of a patientwithout conflicts. Additionally, the invention discloses a processwhereby the target orthodontic virtual arch wire can be redesigned incase of insertion conflicts.

B. Description of Related Art

In orthodontics, a patient suffering from a malocclusion is treated byaffixing brackets to the surface of the teeth and installing an archwire in the slots of the brackets. The arch wire and brackets aredesigned to generate a customized force system that applies forces toteeth, by which individual teeth are moved relative to surroundinganatomical structures into a desired occlusion. There are two basicapproaches to designing an appropriate force system for a patient. Oneis based on a straight arch wire and customized brackets, e.g., Andreikoet al., U.S. Pat. No. 5,447,432. The other is based on off-the shelfbrackets and designing a customized arch wire that has complex bends andtwists designed to move or rotate the teeth in the desired direction.Traditionally, the latter approach has required manual bending of thearch wire by the orthodontist.

In recent years, computer-based approaches have been proposed for aidingorthodontists in their practice. However, these approaches are limitedto diagnosis and treatment planning of craniofacial structures,including the straightening of teeth. For example, U.S. Pat. No.6,648,640 to Rubbert, et al. describes an interactive, computer basedorthodontist treatment planning, appliance design and appliancemanufacturing. A scanner is described which acquires images of thedentition, which are converted to three-dimensional frames of data. Thedata from the several frames are registered to each other to provide acomplete three-dimensional virtual model of the dentition. Individualtooth objects are obtained from the virtual model. Acomputer-interactive software program provides for treatment planning,diagnosis and appliance design from the virtual tooth models. A desiredocclusion for the patient is obtained from the treatment planningsoftware. The virtual model of the desired occlusion and the virtualmodel of the original dentition provide a base of information for custommanufacture of an orthodontic appliance. A variety of possible applianceand appliance manufacturing systems are contemplated, includingcustomized arch wires and customized devices for placement of off-theshelf brackets on the patient's dentition for housing the arch wires,and removable orthodontic appliances.

U.S. Pat. No. 6,632,089 to Rubbert, et al. describes an interactive,software-based treatment planning method to correct a malocclusion. Themethod can be performed on an orthodontic workstation in a clinic or ata remote location such as a lab or precision appliance-manufacturingcenter. The workstation stores a virtual three-dimensional model of thedentition of a patient and patient records. The virtual model ismanipulated by the user to define a target situation for the patient,including a target arch-form and individual tooth positions in thearch-form. Parameters for an orthodontic appliance, such as the locationof orthodontic brackets and resulting shape of an orthodontic arch wire,are obtained from the simulation of tooth movement to the targetsituation and the placement position of virtual brackets. The treatmentplanning can also be executed remotely by a precision appliance servicecenter having access to the virtual model of the dentition. In thelatter situation, the proposed treatment plan is sent to the clinic forreview, and modification or approval by the orthodontist. The method issuitable for other orthodontic appliance systems, including removableappliances such as transparent aligning trays.

Machines for bending orthodontic arch wires have been proposed in theprior art. Andreiko et al. describes an apparatus that takes a straightarch wire and imparts a simple planar arcuate curvature to the wire. Thewire is customized in the sense that the shape of the arc is designedfor a particular patient, but the wire bending apparatus described inAndreiko et al. is limited to a customized bracket approach toorthodontics. In particular, the Andreiko et al. wire bending apparatuscannot produce any complex bends and twists in the wire, e.g., bendsrequiring a combination of translation and rotational motion.

U.S. Pat. No. 6,612,143 to Butscher, et al. describes a robot and methodfor automatically bending orthodontic arch wires, retainers, or otherorthodontic or medical devices into a particular shape. In particular,the disclosure enables the manufacture of custom, highly accurateorthodontic arch wires. Such wires are ideally suited to an archwire-based orthodontic treatment regime based on standard, off-the-shelfbrackets.

If a customized arch wire cannot be properly inserted into the bracketson the dentition of the patient in the malocclusion state, then itseffectiveness may be diminished or lost; and in some instances, the archwire may have to be discarded and a new one may have to be designed.This is likely to increase the treatment time and cost. The art islacking in tools that would enable a practitioner in checking if atarget virtual orthodontic arch wire can be inserted into virtualbrackets placed on the virtual malocclusion dentition of a patientwithout conflicts in advance of actually placing the real arch wire inthe real brackets placed on the dentition of the patient.

The present invention addresses this deficiency in the art and offers amethod and apparatus for checking if a target virtual orthodontic archwire can be inserted into virtual brackets placed on the virtualmalocclusion dentition of a patient without conflicts prior to actuallymanufacturing the arch wire. Additionally, the invention discloses aprocess whereby the target virtual orthodontic arch wire can beredesigned in case of insertion conflicts.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a method is provided for digitallychecking the insertion quality of a customized target virtual arch wiredesigned during treatment planning prior to actually manufacturing thetarget arch wire. The method includes the steps of digitally simulatingthe insertion of the virtual arch wire into the virtual brackets placedup on virtual teeth of a patient in an initial state of interest forchecking if the target virtual arch wire could be inserted into thevirtual brackets without conflicts. The custom arch wire comprisesalternating sequence of straight segments and bent segments, whichtypically give the wire a non-planar shape. For coffect insertion of thearch wire, only the straight segments should go into the bracket slots.In the event that a portion of a bent segment winds up in a bracket slotduring the arch wire insertion into the brackets, then that isidentified as a conflict or a collision. Conflicts are undesirable sincethey cause the arch wire to lose its effectiveness in terms of movingthe patient's teeth from, say malocclusion state to the target state.The straight segments are designed to be longer in length than thecorresponding bracket slots so as to provide some sliding room for thearch wire as the teeth move from malocclusion to the target finishposition.

The method includes the step of selecting a virtual bracket slot as astarting point. Then, the arch wire insertion between the selectedbracket slot and its adjacent neighbour bracket slot is evaluated.Subsequently, the neighbour is designated as the selected bracket slotand the arch wire insertion is evaluated between it and its adjacentneighbour. In this manner, all neighbours on one side of the startingpoint bracket are successively evaluated first, and then on the otherside, so as to evaluate the insertion quality of the entire arch wire.

In another aspect of the invention, a measured force is applied to thevirtual arch wire in an incremental manner for inserting the arch wireinto the selected bracket slot. The incremental process of applying theforce is stopped when the designated virtual arch wire straight segmentis positioned in the corresponding virtual bracket slot within a giventolerance. That means the designated straight segment of the virtualarch wire is properly inserted into the virtual bracket slot without aconflict or a collision.

In another aspect of the invention, even after applying the sufficientforce, if the arch wire insertion into the neighbor causes a conflict ora collision, then the conflict is recorded and the insertion processcontinued until the entire wire is checked out. In case of conflicts,first the arch wire insertion is again checked out with repositioningthe straight segments of the virtual arch wire in the bracket slots.Then, if the repositioning removes all the conflicts, then the arch wireis deemed to have no conflicts. On the other hand, if the conflictspersist, then the optimization step is performed where by the length ofthe straight segment designated for the neighbor bracket slot ismodified to see if the conflict or the collision can be removed. It maybe recalled that a conflict or a collision is created when a portion ofa bent segment gets unavoidably inserted into a bracket slot during thearch wire insertion process. If the conflict or the collision can beremoved in this manner, i.e. by modifying the straight segment length,than that is recorded as a potential arch wire design modification. Onthe other hand, if the conflict persists in spite of the optimization,then the optimization step has failed, and the conflict is recorded atthe neighbor. The length of a straight segment that is in excess of thecorresponding bracket slot length is herein referred to as the ‘designedsliding ways’. Throughout the wire insertion process, at the conclusionof the wire insertion step at a bracket, a running log of the actualsliding ways and the wire insertion depth within the bracket slot ismaintained.

The method described above is summarized as follows:

The method of digitally evaluating the insertion quality of a targetcustom virtual arch wire, comprising the steps of:

(a) obtaining a model of a set of virtual of brackets placed up on thevirtual teeth of a patient in a jaw in an initial state;

(b) obtaining a virtual model of a target custom arch wire designed tobe inserted into said virtual brackets; wherein the custom arch wirecomprises alternating sequence of straight segments and bent segments;wherein each of the straight segments is designated to be inserted intothe slot of a specific virtual bracket from the set of virtual brackets;

(c) selecting a first virtual bracket from the set of virtual brackets;

(d) inserting the first straight segment of the target custom arch wireinto the slot of the first virtual bracket; wherein the first straightsegment is designated for insertion into the slot of the first virtualbracket;

(e) selecting a second virtual bracket from the set of virtual brackets;wherein the second virtual bracket is the neighbor of the first virtualbracket;

(f) inserting the second straight segment of the target custom arch wireinto the slot of the second virtual bracket; wherein the second straightsegment is designated for insertion into the slot of the second virtualbracket; and

(g) evaluating the quality of insertion of the second straight segmentinto the slot of the second virtual bracket.

The above method is then repeated successively for the neighbors in onedirection of the first bracket and then in the other direction. When allthe evaluation is completed for the entire arch wire, then the totalmovement of all the straight segments in the arch wire is computed forusing it as a criterion for selecting a bracket as a starting point inthe arch wire insertion process as described in the next aspect of theinvention.

The method is applied for inserting the arch wire in the brackets placedon the teeth of a patient one jaw at a time. For example, the insertionof the arch wire can be evaluated in the lower jaw first, and then theupper jaw, or vice-versa; as the need may be.

As noted earlier, in the case of a collision or conflict, the arch wiredesign is optimized by modifying the length of the appropriate straightsegment, thereby modifying the design of the target arch wire, so as toattempt to remove the collision. However, it is possible that even aftersuch optimization, the collision or the conflict may persist.

It should be noted that the geometry of the target custom arch wire istypically non-planar in three-dimensions.

The results of the wire insertion process in terms of the virtual archwire and the virtual brackets are continuously displayed to the user

In another aspect, a method is provided for selecting the recommendedstarting point for inserting the virtual arch wire in the virtualbrackets in the initial dentition state of the patient. The methodidentifies the recommended starting point for the arch wire insertion,and simulates and displays the shape of the virtual arch wire afterinsertion into a non-passive state. Each bracket slot is selected as astarting point, and the process for the virtual arch wire insertion intothe virtual brackets is simulated as described above. Finally, theoverall results of the arch wire insertion for all starting points areevaluated. From the evaluation, the recommended starting point for thearch wire insertion is determined as follows:

-   -   (a) Only one starting point without collisions or conflicts:        this bracket slot is recommended as starting point.

(b) Several starting points without collisions or conflicts: the bracketslot requiring the minimum sum of the arch wire actual sliding ways isrecommended for start.

-   -   (c) No starting point without collisions: the arch wire redesign        from the treatment planning perspective is recommended. However,        the user is informed of the bracket slot with the minimum arch        wire insertion depth into the brackets, and a warning is shown;        and the use of the arch wire is left to the user.

The method discussed above is summarized as follows:

The method of determining a recommended starting point for inserting avirtual target custom arch wire into a set of virtual brackets,comprising the steps of:

(a) obtaining a model of a set of virtual of brackets placed up on thevirtual teeth of a patient in a jaw in an initial state;

(b) obtaining a virtual model of a target custom arch wire designed tobe inserted into the virtual brackets; wherein the custom arch wirecomprises alternating sequence of straight segments and bent segments;wherein each of the straight segments is designated to be inserted intothe slot of a specific virtual bracket from the set of virtual brackets;

(c) selecting a virtual bracket from the set of virtual brackets as astarting point;

(d) inserting the designated straight segment of the target custom archwire into the slot of the starting point virtual bracket;

(d) inserting the target custom arch wire successively into the slot ofeach of the virtual brackets remaining from the set of virtual bracketsfirst on one side of the starting point virtual bracket and then theother side; wherein if at least one bent segment or a portion thereof isunavoidably inserted into a bracket slot, then the arch wire insertionis identified as having collision; and otherwise the arch wire insertionis identified as collision-free;

(e) finding the total movement of the straight segments;

(f) repeating steps (c)-(f) until each of the virtual brackets from theset of virtual brackets has been considered as a starting point virtualbracket; and

(g) selecting a starting point virtual bracket having collision-freearch wire insertion and minimal total movement of straight segments asrecommended starting points for arch wire insertion.

In yet another aspect a workstation is provided for storing and runningthe digital simulation software for the arch wire insertion qualitycheck and optimization. The software enables the user to check theinsertion quality of the custom arch wire designed during treatmentplanning phase. When a wire insertion conflict is detected, the softwareattempts, through the optimization software routine, alternate lengthconfigurations for the arch wire straight segment involved in theconflict in order to remove the conflict. If the conflict persists evenafter the optimization step, then the conflict is shown to the user. Inanother aspect, the workstation enables a user in determining the bestbracket to be used as a starting point in the arch wire insertionprocess.

The workstation for determining one or more recommended starting pointsfor inserting a virtual target custom arch wire into a set of virtualbrackets, comprises:

a processor;

a graphical user interface; and

a computer storage medium;

wherein said computer storage medium contains:

-   -   (a) a model of a set of virtual of brackets placed up on the        virtual teeth of a patient in a jaw in an initial state;    -   (b) a virtual model of a target custom arch wire designed to be        inserted into the virtual brackets; wherein the custom arch wire        comprises alternating sequence of straight segments and bent        segments; wherein each of the straight segments is designated to        be inserted into the slot of a specific virtual bracket from the        set of virtual brackets; and    -   (c) instructions for:        -   (i) selecting a virtual bracket from the set of virtual            brackets as a starting point;        -   (ii) inserting the designated straight segment of the target            custom arch wire into the slot of the starting point virtual            bracket;        -   (iii) inserting the target custom arch wire successively            into the slot of each of the virtual brackets remaining from            the set of virtual brackets first on one side of the            starting point virtual bracket and then the other side;            wherein if at least one bent segment or a portion thereof is            unavoidably inserted into a bracket slot, then the arch wire            insertion is identified as having collision; and otherwise            collision-free;        -   (iv) finding the total movement of the straight segments;        -   (v) repeating steps (i)-(iv) until each of the virtual            brackets from the set of virtual brackets has been            considered as a starting point virtual bracket; and    -   (g) selecting a starting point virtual brackets having        collision-free arch wire insertion and minimal total movement of        straight segments as recommended starting points for arch wire        insertion.

BRIEF DESCRIPTION OF THE DRAWINGS

Presently preferred embodiments of the invention are described below inreference to the appended drawings, wherein like reference numeralsrefer to like elements in the various views, and in which:

FIG. 1 is an illustration of an orthodontic care system incorporating ahand-held scanner system. The hand-held scanner is used by theorthodontist or the assistant to acquire three-dimensional informationof the dentition and associated anatomical structures of a patient andprovide a base of information to diagnose and plan treatment for thepatient.

FIG. 2 is a screen shot showing the virtual model of the teeth of apatient in malocclusion state.

FIG. 3 is a screen shot of the virtual model of the teeth of a patientin the malocclusion state the same as in FIG. 2. Additionally, FIG. 3shows the virtual brackets placed up on the virtual teeth of thepatient.

FIG. 4 is a screen shot from an orthodontic workstation showing thecomputer model of the patient's teeth positioned in a target or desiredcondition. FIG. 4 also shows the various parameters by which theorthodontist can adjust the shape of the arch, the distance between theteeth, the distance between the molars, and other parameters, so as toprovide a unique and customized target situation for the patient.

FIG. 5 is another screen shot showing the computer model of thepatient's teeth in a target situation, also showing the numerousparameters available to the orthodontist to customize the toothposition, orientation, angulation, torque, and other parameters on atooth by tooth basis for the target archform.

FIG. 6 is another screen shot showing a front view of the targetsituation and additional parameters available to the orthodontist formoving teeth relative to each other in planning treatment for thepatient.

FIG. 7 is a screen shot of a target situation for the patient showingthe virtual tooth in a target position, a set of virtual brackets placedon the teeth, and a virtual arch wire.

FIG. 8 is a simplified illustration of a set of teeth showing the originof a coordinate system that is used to calculate bracket location for aset of brackets, in three dimensions, for a patient. The bracketlocation for the teeth in a target situation determines the shape of anorthodontic arch wire.

FIG. 9 is an illustration showing the vectors drawn from the origin ofthe coordinate system to the center of the brackets.

FIG. 10 is a perspective view of an orthodontic bracket.

FIG. 11 shows the origin, the position vector, and the X and Y unitvectors which indicate the orientation of the bracket slot. It alsoshows the scale (in units of millimeters) which gives absolute locationand orientation information for the bracket slot.

FIG. 12 shows the normal vector Y for a particular bracket, thetangential vector X, the tangential distance T_(d) and antitangentialdistance AT_(d).

FIG. 13 shows in matrix form the values for an individual bracket whichdescribe the location of the bracket and its orientation, which are usedto generate the commands for the robot to form the orthodontic archwire.

FIG. 14 is an illustration of a set of points P1, P2, P3, . . . PN whichrepresent a set of bending points associated with individual bracketsfor a patient in a target situation. The location of the points in thethree-dimensional coordinate system is known.

FIG. 15 is an illustration of a section of wire between points P1 and P4in which a bend is placed between points P2 and P3.

FIG. 16 shows the arch wire designed for the target state throughtreatment planning.

FIG. 17 shows a version of FIG. 3 where simply the virtual brackets areshown placed in the malocclusion state the same as in FIG. 3, and thevirtual teeth are hidden from the view.

FIG. 18 shows a flow chart for carrying out the virtual arch wireinsertion check and optimization simulation, according to a preferredembodiment of the invention. The simulation process is iterative.

FIG. 19 illustrates the virtual arch wire insertion in a virtualneighbour bracket slot without collision, according to a preferredembodiment of the invention. The results of incremental iteration stepsto simulate the deformation of the virtual arch wire are shown.

FIG. 20 illustrates the virtual arch wire insertion in a virtualneighbour bracket slot with collision, according to a preferredembodiment of the invention.

FIG. 21 shows a flow chart for selecting the best starting point forinserting the virtual arch wire into the brackets, according to anotherpreferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Overview

FIG. 1 is an illustration of an orthodontic care system 10 incorporatinga scanner system 12. The scanner system 12 includes a hand-held scanner14 that is used by the orthodontist or his assistant to acquirethree-dimensional information of the dentition and associated anatomicalstructures of a patient. The images are processed in a scanning node orworkstation 16 having a central processing unit, such as ageneral-purpose computer. The scanning node 16, either alone or incombination with a back-office server 28, generates a three-dimensionalcomputer model 18 of the dentition and provides the orthodontist with abase of information for diagnosis, planning treatment, and monitoringcare for the patient. The model 18 is displayed to the user on a monitor20 connected to the scanning node 16.

As noted above, the scanner system 12 is optimized for in-vivo scanningof teeth, or alternatively, scanning a plaster model of the teeth and/oran impression of the teeth.

The orthodontic care system consists of a plurality of orthodonticclinics 22 which are linked via the Internet or other suitablecommunications medium 24 (such as the public switched telephone network,cable network, wireless network, etc.) to a precision appliance servicecenter 26. Each clinic 22 has a back office server work station 28having its own user interface, including a monitor 30. The back officeserver 28 executes an orthodontic treatment planning software program.The software obtains the three-dimensional digital data of the patient'steeth from the scanning node 16 and displays the model 18 for theorthodontist. The treatment planning software includes features toenable the orthodontist to manipulate the model 18 to plan treatment forthe patient. For example, the orthodontist can select an archform forthe teeth and manipulate individual tooth positions relative to thearchform to arrive at a desired or target situation for the patient. Thesoftware moves the virtual teeth in accordance with the selections ofthe orthodontist. The software also allows the orthodontist toselectively place virtual brackets on the tooth models and design acustomized virtual arch wire for the patient given the selected bracketpositions. Alternately, a scan may be taken of the patient's dentitionwith the brackets already placed on the patient's teeth. In this case avirtual model is created from the scan data, using the system 10software which may be placed in the scanning node 16, the back officeserver work station 28 or the central server 32, such that the teeth andthe brackets can be manipulated as individual virtual objects. In thiscase the practitioner or the user designs the customized arch wire usingthe positions of the brackets as those already placed on the patient'steeth. When the orthodontist has finished designing the orthodonticappliance for the patient, digital information regarding the patient,the malocclusion, and a desired treatment plan for the patient is sentover the communications medium to the appliance service center 26. Acustomized orthodontic arch wire and a device for placement of thebrackets on the teeth at the selected location is manufactured at theservice center and shipped to the clinic 22.

As shown in FIG. 1, the precision appliance service center 26 includes acentral server 32, an arch wire manufacturing system 34 and a bracketplacement manufacturing system 36. For more details on these aspects ofthe illustrated orthodontic care system, the interested reader isdirected to the patent application of Rüdger Rubbert et al., filed Apr.13, 2001, entitled INTERACTIVE AND ARCHWIRE-BASED ORTHODONTIC CARESYSTEM BASED ON INTRA-ORAL SCANNING OF TEETH, Ser. No. 09/835,039, nowissued as U.S. Pat. No. 6,648,640, the entire contents of which areincorporated by reference herein.

A virtual model of the dentition of the patient is created throughscanning. This may be done through in-vivo scanning of the patient, orthrough scanning of the physical model of the patient. Individualvirtual tooth objects are created from the virtual dentition model. Thedigital models of the brackets, arch wires and other orthodonticappliances can be stored in the workstation storage in the form oflibraries, and retrieved during treatment planning as needed. Thedigital models of the brackets can be created from scanning individualbrackets. Often, scanning of the patient's dentition is done where thebrackets are already mounted on the patient's teeth. In this case, thevirtual model comprises individual virtual tooth objects and individualvirtual bracket objects. The combination of the displayed set of virtualorthodontic brackets, together with the virtual orthodontic arch wire,presents to the user a customized virtual orthodontic appliance. Thevirtue of the customized virtual orthodontic appliance is that it can bestudied, modified, shared between two computers, and transportedelectronically over a communications medium for fabrication of theorthodontic appliance. The treatment planning software is essentially aspecialized CAD/CAM system that allows the design of virtually anyconfiguration of tooth objects, bracket objects, wire objects and otherappliances and objects. Because these objects exist as independentmathematical objects, they can be selectively displayed together oralone. For example, the treatment planning software displays an icon orbutton on the user interface that allows the user to select or deselectthe teeth, wires, brackets or virtual objects or appliances, as desired.For example, the teeth and arch wire can be displayed together with thebrackets deleted from the user interface. The orthodontist can thenselect an individual tooth object, move it in three dimensions, and themovement of the tooth carried over to a repositioning of the bracket inthree dimensions and a changing of the shape of the arch wire.

Furthermore, while the above process of creation of tooth models hasbeen described in conjunction with the scan data from the hand-heldscanner, this is not required. The separation of tooth objects can beperformed with any three-dimensional model of the teeth, regardless ofhow the three-dimensional model is obtained. The three-dimensional modelcould be acquired from a CT scan, a laser scan from a plasterimpression, or otherwise.

Treatment Planning

The virtual model of the patient's dentition, and the individual toothobjects created as explained above, provide a base for diagnosticanalysis of the dentition and treatment planning. Treatment planningsoftware is provided on the workstation of the orthodontic clinic, andpossibly at other remote locations such as the precision appliancecenter of FIG. 1. The treatment planning software can be considered aninteractive, computer-based computer aided design and computer aidedmanufacturing (CAD/CAM) system for orthodontics. The apparatus is highlyinteractive, in that it provides the orthodontist with the opportunityto both observe and analyze the current stage of the patient'scondition, and to develop and specify a target or desired stage. Ashortest direct path of tooth movement to the target stage can also bedetermined. Further, the apparatus provides for simulation of toothmovement between current and target stages. For further details ontreatment planning, refer to the previously mentioned patent applicationof Rüdger Rubbert et al., filed Apr. 13, 2001, entitled INTERACTIVE ANDARCHWIRE-BASED ORTHODONTIC CARE SYSTEM BASED ON INTRA-ORAL SCANNING OFTEETH, Ser. No. 09/835,039, now issued as U.S. Pat. No. 6,648,640, theentire contents of which are incorporated by reference herein.

FIG. 2 is a screen shot showing the virtual model of the teeth 110 of apatient in malocclusion state.

FIG. 3 is a screen shot of the virtual model of the teeth 110 of apatient in the malocclusion state the same as in FIG. 2. Additionally,FIG. 3 shows the virtual brackets 210 which are placed up on the virtualteeth 110 of the patient. The placement of the virtual brackets on thevirtual teeth can be as a result of the treatment planning using thesoftware provided in the system 10 of FIG. 1. Alternately, the placementof the virtual brackets on the virtual teeth can be obtained through thescanning of the patient's dentition where the practitioner has alreadyplaced the brackets up on the teeth of the patient.

FIG. 4 is a screen shot from an orthodontic workstation showing thecomputer model of the patient's teeth objects 312 positioned in a targetor desired condition. The illustration is the result of the userselecting an archform for the patient from a known type of archform(e.g., Roth), and the computer placing the teeth along the arch selectedby the user. This is executed by placing the virtual brackets theorthodontist placed on the virtual teeth along the curve selected by theorthodontist. The brackets are omitted from FIG. 4, but are shown inFIG. 5. The software allows the orthodontist to change many variables inthe target situation, simply by entering new values in the slide linearea 320 of the screen display, by mouse operation of up and down arrowsto scroll through available values, or by mouse operation of a bar tochange the values, or other similar technique. FIG. 4 shows some of theparameters by which the orthodontist can adjust the shape of the arch,the distance between the teeth, the distance between the molars, andother parameters, so as to provide a unique and customized targetsituation for the patient.

FIG. 5 is another screen shot showing the computer model of thepatient's teeth in a target situation, also showing the numerousparameters available to the orthodontist to customize the toothposition, orientation, angulation, torque, and other parameters on atooth-by-tooth basis for the target archform. Virtual brackets 322 arepositioned on the tooth objects 312 at the location where the userplaced the landmarks. A virtual arch wire 324 passes through the slotsin each virtual bracket.

FIG. 6 is another screen shot showing a front view of the targetsituation and additional parameters available to the orthodontist forsimulating the movement and positioning of teeth relative to each otherin planning treatment for the patient. For example, in FIG. 6, thecursor is moved onto the virtual tooth 41 (in the tooth numberingconvention) and the mouse is clicked. Tooth 41 is then highlighted. Ifthe orthodontist wants to extract that tooth, then the tooth could beextracted in the simulation. Alternatively, tooth 41 could be rotatedabout any of three axis of rotation, moved in the X, Y or Z direction,or a larger or smaller gap could be created between teeth.

FIG. 7 shows the target situation for the upper arch, with the virtualbrackets 322 in place. The orthodontist can adjust the bracket 322position, arch wire shape 324, or tooth 312 position, on a tooth bytooth basis to thereby optimize treatment planning for the patient.

The result of the treatment planning is the generation of a set ofbracket placement positions, if already not given, and the display onthe monitor of the shape of a customized orthodontic arch wire to treatthe malocclusion.

Arch Wire Design

The arch wire design, which dictates the shape of an arch wire resultingfrom the treatment planning, will now be discussed in conjunction withFIGS. 8-15. The arch wire design includes a set of matrices, one matrixfor each bracket in the arch of the patient. Each matrix consists of acombination of a vector of location of a point on the bracket and amatrix of orientation, indicating the orientation of the bracket inthree-dimensional space. Both the vector of location and the matrix oforientation are based on the position of the brackets on the teeth whenthe teeth are in a target situation. The target situation is developedby the orthodontist from the scan of the dentition and the execution ofa treatment planning using the treatment planning software at theclinic.

FIG. 8 illustrates the target situation for one arch 420 of a patient.The target situation is a three dimensional virtual model of the teeth422 in which virtual brackets 424 are placed, for example, on the labialsurface of the teeth. A coordinate system is defined for the arch 420having an origin 426. The coordinate system is in three dimensions, withthe X and Y dimensions lying in the plane of the arch and the Zdirection pointing out of the page. The location of the origin 426 isnot particularly important. In the illustrated embodiment, an average“mass” is assigned to each virtual tooth in the arch, and a center of“mass” is calculated for the arch 420 and the original 426 is located atthat center.

As shown in FIGS. 9 and 10, a vector of location 428 is defined for eachbracket. The vector 428 extends from the origin 426 to the center of theslot 430 in the bracket along the wall 432 of the bracket slot, i.e., topoint 434. The vector of location consists of the X, Y and Z coordinatesof the point 434 in the defined arch coordinate system.

The orientation matrix consists of a 3×3 matrix of unit vectors of theform:X₁ Y₁ Z₁X₂ Y₂ Z₂X₃ Y₃ Z₃  (1)

where X₁, X₂ and X₃ are the X, Y and Z components of the X unit vectorshown in FIG. 10; Y₁, Y₂ and Y₃ are the X, Y and Z components of the Yunit vector shown in FIG. 10; and Z₁, Z₂ and Z₃ are the X, Y and Zcomponents of the Z unit vector shown in FIG. 10. As noted above, thematrix for each bracket thus consists of the combination of the 3×3orientation matrix and the position matrix, and is thus as follows:X₁ Y₁ Z₁ XX₂ Y₂ Z₂ YX₃ Y₃ Z₃ Z0 0 0 1  (2)where X, Y and Z in the right hand column of entries is the positionvector.

The arch wire design also includes an antitangential value and atangential value for each bracket. The antitangential value consists ofthe distance from the center of the bracket slot (point 434) to a pointdefining the terminus of the previous bend in the wire. The tangentialvalue consists of the distance from the center of the bracket slot tothe point defining the terminus of the next bend in the wire. The archwire design also consists of the thickness of the wire, as measured inthe direction of the Y unit vector in FIG. 10.

With reference to FIG. 11, an example of the 4×4 matrix 2) for a rearmost molar of a patient will be described. Figure shows the origin 426,the position vector 428, and the X and Y unit vectors which indicate theorientation of the bracket slot. FIG. 11 also shows the scale (in unitsof millimeters) which gives absolute location and orientationinformation for the bracket slot. Here, we assume in the example thatthere is no Z component to the tangential vector X or the normal vectorY.

FIG. 12 shows the tangential distance T_(D) and the antitangentialdistance AT_(D) as measured along the centerline of the arch wire. Theresulting matrix is shown in FIG. 13.

From a set of the matrices as shown in FIG. 13 comprising all thebrackets in the arch, the program extracts a series of line segments inthree dimensional space, which are defined by the terminus of theantitangential and tangential distances for each bracket slot. The setof line segments 440 is shown in FIG. 14. The line segments are definedby a set of points P1, P2, P3. . . Pn having known three dimensionalcoordinates due to the known location of the bracket slots and the knowntangential and antitangential distances. The line segments can also bedefined as a set of vectors having a location for the head of the vectorand a magnitude and orientation in three directions. The followingdiscussion will use the set of points P1, P2, P3. . . PN. In FIG. 14,the slashes 442 indicate the end points of the bracket slot 430 of FIG.10.

The bends need to be placed in the wire before point P1, between pointsP2 and P3, between points P4 and P5, etc., that is, between the bracketslots. The slot-to-slot bends of the complete arch wire are bent sectionby section. The straight wire sections 440 between the bends have to fitto the bracket slots. The bend is indicated at 444 in FIG. 15. Once thearch wire design is complete from the treatment planning view point, itis subjected to the insertion quality check, and further optimization ifnecessary, as described below.

Arch Wire Insertion Evaluation and Design Optimization

Prior to actually manufacturing the target arch wire designed abovethrough treatment planning, it is important to check if the targetvirtual arch wire could be inserted into the virtual brackets placed onthe virtual dentition of the patient in the initial state of interestwithout conflicts or collisions. As noted earlier the customized archwire consists of alternating sequence of straight segments and custombent segments. Customized bends may comprise bends and twists, which maybe complex and typically make the arch wire shape non-planar. Straightsegments are designed to go in the bracket slots and the bent segmentsbetween the brackets. If during the arch wire insertion process, if thewire cannot be inserted into a bracket slot without keeping a portion ofthe bet segment out of the bracket slot, then a conflict or a collisionis created. In other words, the arch wire insertion where a portion of abent segment gets in the bracket slot is called a conflict or acollision. One or more conflicts diminish the effectiveness of the archwire in moving the teeth from malocclusion to the target positions. Theinitial state might be the malocclusion state or an intermediate stateduring the course of the treatment. Without the loss of generality, thefollowing discussion will primarily assume the initial state to be themal occlusion state. In the event the target virtual arch wire wouldcause conflicts violating the effectiveness of the designed target archwire, then it is important to know the location and extent of theconflicts so that corrective options to remove the conflicts can beevaluated and exercised as and when appropriate so as to optimize thedesign of the arch wire. The instant invention provides thesecapabilities. The instant invention provides the capabilities toindicate and visualize conflicts for the whole arch wire and on thelevel of individual brackets, so that further judgments and measurementscan be applied easily. The instant invention reliably indicates “noconflict” or “possible conflicts”. That means automated judgmentregarding “conflict free insertion” or indication of needed attention tosolve the conflicts through alternate and optimized design of the targetarch wire. Furthermore, in a preferred embodiment, the inventioncalculates and shows a recommended starting point for the arch wireinsertion, and simulates and displays the shape of the virtual arch wireafter insertion into a non-passive state.

As discussed above, in order to achieve the treatment objective, thearch wire is bent in a manner such that it comprises alternatingstraight segments and bent segments. When the target arch wire isligature tied to the bracket slots, it enables, in the relaxed state,movement of the teeth to the target positions. A preferred embodiment ofthe invention digitally simulates the insertion of the virtual arch wireinto the virtual brackets placed up on virtual teeth of a patient inmalocclusion or any initial state of interest. The digital simulationtakes into account the following requirements and constraints that wouldbe applicable with respect to the actual arch wire when inserted intothe actual brackets bonded to the patient's teeth. The ligature tying ofthe arch wire to the brackets placed on the patient's teeth in themalocclusion state (or any other state of interest) should be done insuch a way that the arch wire may conduct the necessary movements duringthe course of the treatment while satisfying the following conditions.When ligature tying the arch wire, each straight part of the arch wirehas to be placed in the designated bracket slot in the malocclusion orinitial state. In addition, the arch wire must be able to move duringthe course of the treatment to such a distance that the target teethposition can be reached without having the arch wire getting stuck orinterlocked within or at the edges of the brackets. As describedearlier, these straight wire parts or segments are incorporated into thearch wire design, and have lengths per the target arch wire designresulting from the treatment planning.

According to a preferred embodiment of the invention, computer softwarefor the arch wire insertion quality check, and the arch wire designalteration and optimization when necessary, is provided in the centralserver 32 of FIG. 1. However, one skilled in the art would appreciatethat this simulation software can as well be placed in the back officeserver workstation 28, the scanning node 16 or any other workstation inthe system 10. One of the tasks of the simulation software routinedescribed herein is to simulate the ligature tying of the virtual archwire and to check whether the designed virtual arch wire can be ligaturetied to the brackets under the given constraints. In summary, theessential steps carried out by the simulation software are: (a) thenumerical calculation of the deformation of the virtual arch wire or thearch wire segments between the bracket slots, and (b) the determinationof the resulting relative positions of the straight segments or theactual sliding ways with respect to the brackets at the malocclusion andthe realization of a balance between the segments by shifting the archwire along the bracket slots within the tolerable range. The arch wireof the target stage designed as previously described serves as the basisor the starting point for the insertion quality check and optimization.This arch wire is represented by a sequence of segments. These segmentsare an alternating sequence of straight parts or segments and partshaving bends, twists or complex bends which may be specified accordingto a Bezier spline. All of the arch wire segment lengths used insimulation initially exactly match the wire design described earlier.The arch wire design is represented in the form of a data file. When thearch wire is manufactured, this data file in its final form after theinsertion check and optimization simulation guides the robot, whichbends the arch wire in the desired shape. The insertion simulation takesinto account elastic and pseudo-plastic deformations of the wire.

FIG. 16 shows a virtual arch wire designed for the target state per thetreatment planning described earlier. The virtual target arch wire inFIG. 16 comprises alternating straight segments (e.g. straight segments510, 512 and 514) and bent segments (e.g. bent segments 511 and 513).There is one straight segment per bracket, and each straight segment isdesignated for insertion into a specific bracket slot.

FIG. 17 shows a modified view of the screen shot in FIG. 3. FIG. 17shows the virtual brackets (e.g. the virtual brackets 550, 552 and 554)(the virtual brackets 210 in FIG. 3) placed in the malocclusion state ofthe patient. The virtual teeth (the virtual teeth 110 in FIG. 3) arehidden from the view in FIG. 17.

FIG. 18 shows a flow chart 600 for carrying out the virtual arch wireinsertion quality check and the arch wire optimization simulationaccording to a preferred embodiment of the invention. The simulationprocess is iterative.

At step 610, a virtual bracket slot is selected as a starting point,e.g. the slot on the virtual bracket 550 in FIG. 17. This may be a userselected virtual bracket slot, or alternately, automatically selected bythe simulation software. Then, the straight segment of the virtual archwire, e.g. the straight segment 510 in FIG. 16, designated for theselected bracket slot is inserted into the selected bracket slot; andthe possible movements of the virtual arch wire in the tangential andantitangential directions are computed. The insertion of the straightsegment of the virtual arch wire in the selected virtual bracket slot isdone in a manner such that it digitally simulates the ligature tying ofthe virtual arch wire to the selected virtual bracket slot which permitssliding movements of the virtual arch wire within the selected virtualbracket slot, but prevents the virtual arch wire from popping out of theselected virtual bracket slot. Then, the tangential direction isselected for the arch wire insertion evaluation. The selection of thetangential direction for further evaluation is arbitrary at this point.One can also start the evaluation process by initially selecting theantitangential direction.

Next, at step 612, a check is made to determine if there is a neighborbracket slot in the selected direction? If the answer at step 612 is inthe affirmative, then the process moves to step 614; otherwise to step620.

At step 614, the virtual arch wire, e.g. the straight segment 512 inFIG. 16, is inserted in the virtual neighbor bracket slot, e.g. the sloton the virtual bracket 552 in FIG. 17; and estimates are made of thedeformation, the forces and the moments on the virtual arch wire segmentbetween the selected bracket slot and the neighbor bracket slot. Theforce and moment are required to bring the unrestrained virtual archwire into an alignment with the virtual neighbor bracket slot. The forceis applied incrementally depending up on the distance between theselected and the neighbor virtual brackets and the distance from thevirtual arch wire end (in the direction of the neighbor bracket) to thevirtual neighbor bracket. The magnitude of the force and the moment andthe point on the virtual arch wire where the force is applied, whichmimic insertion of the actual arch wire into the actual bracket slot,are calculated incrementally and iteratively.

The initial force is calculated using Eq. (1).

$\begin{matrix}{{\overset{->}{F} = \frac{2*\overset{->}{D}}{( \frac{L}{10.0} )^{2}}};} & {{Eq}.\mspace{14mu}(1)}\end{matrix}$

where:

-   -   {right arrow over (F)}—force;    -   {right arrow over (D)}—distance from the virtual arch wire end        (in the direction of the neighbor virtual bracket) to the        neighbor virtual bracket; and    -   L—length of the virtual arch wire between the two virtual        brackets.

Then, the virtual arch wire distortion under the applied force andmoment is determined and their (force and moment) value and directionare corrected with the new distance of the unrestrained virtual archwire end to the target. The new value of the force from the previousvalue is computed using Eq. (2).

$\begin{matrix}{{{\overset{->}{F}}_{n + 1} = {{\overset{->}{F}}_{n} + {\overset{->}{d} \cdot \frac{{\overset{->}{F}}_{n}}{{\overset{->}{D}}_{n}} \cdot \gamma}}};} & {{Eq}.\mspace{14mu}(2)}\end{matrix}$where:{right arrow over (F)}_(n)—force at the incremental step n;{right arrow over (F)}_(n+1)—new force at the incremental step n+1;{right arrow over (D)}_(n)—movement of virtual arch wire under {rightarrow over (F)}_(n);{right arrow over (d)}—actual distance from the virtual arch wire end(in the direction of the neighbor virtual bracket) to the neighborvirtual bracket;λ—damping factor to avoid overshooting; 0<λ<1.0.

During the force and moment calculation it is assumed that the forces atthe brackets have only normal component. Then, the force and momentdirections are corrected accordingly as the incremental force isapplied.

In order to calculate the elastic deformation from the applied force andmoment, a linear bending theory is used. The displacement of the pointwhere the force is applied is calculated from an integration of thedisplacement of the wire cross section over the length of the wiresegment. The displacement at a given point results from the locallyexerted forces per Eq. (2). where large moments are exerted, it followsa large curvature of the virtual arch wire, and with smaller moments aproportionate smaller one.

The advantage of the incremental and iterative approach is that thepseudo-plastic deformations of the virtual arch wire segment can also beeasy accounted for in the simulation. Therefore, above an empiricallydetermined limit of material tension, the affected areas of the virtualarch wire do not react with further force or moment increase to furtherdeformation. Pseudo-plastic deformation plays an important role with theNiTi arch wires.

According to a preferred embodiment of the invention, in order tocalculate the deformation from the local moment exerted on the virtualarch wire cross-section (forces may be neglected), the moment isdecomposed into three parts: a torsional moment and two bending momentsalong the main axis. An independent description of these three momentsis possible for purely elastic deformations. The deformation can also beexpressed using the three angles representing the movement of the archwire cross section. These angles are calculated from the followingequations:

$\begin{matrix}{{\alpha_{x} = \frac{M_{x} \cdot h}{I_{x} \cdot E}};} & {{Eq}.\mspace{14mu}(3)} \\{{\alpha_{y} = \frac{M_{y} \cdot h}{I_{y} \cdot E}};} & {{Eq}.\mspace{14mu}(4)} \\{{\alpha_{z} = \frac{M_{z} \cdot h}{I_{z} \cdot G}};} & {{Eq}.\mspace{14mu}(5)}\end{matrix}$

where:

-   -   Mx, My—Bending moments;    -   Mz—Torsional moment;    -   Ix, Iy, Iz—Moment of inertia of the area in the respective        directions;    -   h—Thickness of the cross section of the virtual arch wire;    -   E—modulus of elasticity; and    -   G—modulus of transverse elasticity.

The incremental process of applying the force is stopped if thedesignated virtual arch wire straight segment is aligned with thecorresponding virtual bracket slot within a given tolerance. That meansthe designated straight segment of the virtual arch wire is be properlyinserted into the virtual bracket slot without conflict or collision. Onthe other hand, even after applying the sufficient force, the arch wireinsertion in the neighbor causes a conflict or a collision, then theoptimization step is performed where by the length of the straightsegment designated for the neighbor bracket slot is modified, i.e.increased or decreased, to see if the conflict or the collision can beremoved. It may be recalled that a conflict or a collision is createdwhen a portion of a bent segment gets inserted into a bracket slotduring the arch wire insertion process. If the conflict or the collisioncan be removed in this manner, i.e. by modifying the straight segmentlength, than the new or actual sliding way is recorded. On the otherhand, if the conflict persists, then the optimization step has failed,and the conflict is recorded at the neighbor.

Next, at step 616, a determination is made for collision in the neighborbracket slot:

(a) No collision: If a collision is not detected without the need foroptimization to modify the straight segment, then the original actualsliding way is marked acceptable and recorded without change. On theother hand, if a potential collision was removed through optimization,then the new (modified) sliding way is recorded, and the possiblesliding movements of the arch wire in the tangential and antitangentialdirections are corrected.

(b) Collision: If a collision is detected which could not be correctedthrough optimization, then the depth of the insertion of the arch wirein the neighbor bracket slot as well as the original sliding way arerecorded.

FIG. 19 presents an enlarged view of a portion of the illustrationbetween the virtual bracket 550 and the virtual bracket 552 in FIG. 17;and the straight segments 510 and 512, and the bent segment 511 of thearch wire in FIG. 16. FIG. 19 illustrates insertion of the straightsegment 512 into the slot of the virtual bracket 552 in incrementalsteps 580, 582 and 584. As can be seen from FIG. 17, the straightsegment 512 is inserted into the slot of the virtual bracket 552 withoutconflict or collision. The results of incremental iteration steps tosimulate the deformation of the virtual arch wire are shown. Due to thesuccessively corrected forces and moments applied during the simulatedinsertion process, the virtual arch wire end approaches the virtualneighbour bracket slot the placement of which corresponds to themalocclusion state of the patient. Virtual teeth are hidden from view inFIG. 19.

Next, at step 618, the neighbor is designated as the selected bracketslot and movements in the tangential and antitangential directions arecomputed. The process then moves back to step 612.

FIG. 20 presents an enlarged view of a portion of the illustrationbetween the virtual bracket 552 and the virtual bracket 554 in FIG. 17;and the straight segments 512 and 514, and the bent segment 513 of thearch wire in FIG. 16. FIG. 19 illustrates insertion of the straightsegment 514 into the slot of the virtual bracket 554 in incrementalsteps 590 and 592. As can be seen from FIG. 17, the straight segment 514is inserted into the slot of the virtual bracket 554, which is showntransparent for the illustration purposes, with a conflict or collisionas a portion of the bent segment 513 gets inserted into the slot aswell. Optimization to remove the conflict or collision was unsuccessfulin this case, so the conflict or collision was recorded for the virtualbracket 554. Here again, the virtual teeth are hidden from the displayin FIG. 20.

At step 620, a check is made to determine if the selected direction forevaluation is antitangential. If the answer at step 620 is in thenegative, the process moves to step 622; otherwise to step 624.

At step 622, the starting point bracket slot is reset as the selectedbracket slot; and the antitangential direction is selected for the archwire insertion evaluation. The process then moves back to step 612.

In this manner, the simulation process is repeated until the targetvirtual arch wire insertion is evaluated for the entire virtual archwire with respect to all the virtual brackets which are placedcorresponding to the malocclusion state of the patient.

At step 624, the results of the arch wire insertion simulation areevaluated as follows:

(a) In case of no collisions or conflicts, including the collisions orconflicts which could be removed with modified straight segments, thesum of the necessary actual sliding ways in all of the virtual bracketslots is computed; and the starting point and the placement of the archwire are recorded as acceptable for the arch wire insertion.

(b) In case of non-resolvable collisions, the starting point is recordedas unacceptable for the arch wire insertion; and the sum of the virtualarch wire insertion depths into each virtual bracket slot as well as thesum of the necessary sliding ways are computed and recorded forpotential use in redesigning the arch wire.

Next, FIG. 21 shows a flow chart 800 for selecting the best startingpoint for inserting the virtual arch wire according to another preferredembodiment of the invention. In order to select the best starting point,basically, each virtual bracket is selected as a potential startingpoint for evaluating the quality of the virtual arch wire insertion, andthe process of FIG. 18 is repeated.

At step 810, a virtual bracket slot is selected as a starting point.

Next, at step 812 the results of the virtual arch wire insertion areevaluated for the starting point bracket slot. The entire evaluationprocess described in the flow chart of FIG. 18 is used at step 812.

Next, at step 814, a determination is made whether all bracket slotshave been considered as a starting point or not? If the answer is in thenegative, the process moves to step 816; otherwise to step 818.

At step 816, another virtual bracket slot is selected as a startingpoint; and the process is repeated from step 812.

At step 818, overall results of the arch wire insertion for all startingpoints are evaluated. From the evaluation, the best starting point forthe arch wire insertion is determined as follows:

-   -   (a) Only one starting point without collisions or conflicts:        this bracket slot is recommended as starting point.    -   (b) Several starting points without collisions or conflicts: the        bracket slot requiring the minimum sum of the arch wire actual        sliding ways is recommended for start.    -   (c) No starting point without collisions: the arch wire redesign        from the treatment planning perspective is recommended. However,        the user is informed of the bracket slot with the minimum arch        wire insertion depth into the brackets, and a warning is shown;        and the use of the arch wire is left to the user.

In summary then, the invention disclosed herein offers three potentialoutcomes for the arch wire custom designed during the treatment planningregarding the wire's capability for insertion into the brackets placedon the dentition of a patient in malocclusion state through thesimulation exercise of the virtual arch wire insertion evaluation: (a)the arch wire is capable of insertion without conflicts or collisions,(b) the arch wire as designed poses conflicts which van be overcomethrough the automatic optimization of the straight segments of the archwire by the software, and (c) the arch wire as designed poses conflictswhich cannot be overcome through the automatic optimization of thestraight segments of the arch wire. Additionally, the inventiondisclosed herein enables the user in automatically selecting the bestinsertion starting point as to the bracket in the event that there areno conflicts either to begin with or through the redesign of the archwire through optimization.

In another embodiment of the invention, the forces and moments at thevirtual brackets are estimated by the arch wire insertion evaluationsoftware routine, and the user is informed about the applied forces andmoments indicating critical areas, e.g., violation of biologicalconstrains or treatment objectives, during the treatment planning andarch wire design process.

Additionally, the invention lets the user evaluate other options for thearch wire design. For example, the user has the option to manipulate thewire outline by manually changing the sliding ways to remove collisions,which are not solved automatically. If this is not possible, thetreatment can be planned in stages; and the arch wire can be designedand evaluated for the insertion quality accordingly. For example, thepractitioner may prefer using limit arch wires (e.g. 50% of target). Asanother option, the practitioner may evaluate the scenario of partialligature tied in to the bracket for a defined period of time. Thepractitioner may evaluate yet another option of repositioning thebrackets or re-bonding the brackets in the case where the brackets arealready placed on the teeth of the patient. The treatment planningsoftware in combination with the novel arch wire insertion evaluationsoftware described herein enables the user or the practitioner inevaluating the variety of options described above; and there byselecting the option best suited to the patient. One skilled in the artwould appreciate that the over all treatment options, including the archwire design and implementation, discussed above are for example purposesonly, and not meant to present an exhaustive list for application of theinstant invention.

Because the hand-held scanner allows for scans of the dentition in amatter of minutes, the scanner becomes an important tool in monitoringtreatment. As the treatment progresses, the movement and position of theteeth during treatment can be quantified with a high degree of precisionby taking scans of the patient's dentition with brackets mounted on theteeth of the patient. The orthodontist can discern during treatment thatcorrections in the wire need to be made, for example due to biologicalinfluences affecting tooth movement. The treatment planning software onthe workstation displays the current situation, and also the targetsituation. A new customized arch wire is designed and evaluated forinsertion quality on the computer. The relevant information for makingthe new arch wire is sent to the precision appliance service center anda new arch wire is manufactured and shipped to the clinic.

Finally, The complete design of the arch wire is provided in a CNC datafile for the arch wire-bending robot located at the precision appliancecenter 26 of FIG. 1. The robot manufactures the custom arch wire inaccordance with the final design. The robot has six degrees of freedomin movement, so complex, non-planar bends in the arch wire can berealized. Additionally, a transfer tray is manufactured to assist theorthodontist in placing the brackets at the proper location on thedentition of the patient. The transfer tray, brackets and arch wire areshipped to the orthodontist's clinic 22. The orthodontic appliance isthen applied to the patient and treatment commences. For further detailson arch wire design and manufacturing, refer to the patent applicationof Butscher et al., filed Apr. 13, 2001, entitled ROBOT AND METHOD FORBENDING ORTHODONTIC ARCHWIRES AND OTHER MEDICAL DEVICES, Ser. No.09/834,967, now issued as U.S. Pat. No. 6,612,143, the entire contentsof which are incorporated by reference herein.

Presently preferred and alternative embodiments of the invention havebeen set forth. Variation from the preferred and alternative embodimentsmay be made without departure from the scope and spirit of thisinvention.

1. A method of digitally evaluating the insertion quality of a targetcustom virtual arch wire, comprising the steps of: (a) obtaining a modelof a set of virtual of brackets placed up on virtual teeth of a patientin a jaw in an initial state; wherein each of said set of virtualbrackets has a slot; (b) obtaining a virtual model of a target customarch wire designed to be inserted into said virtual brackets; whereinsaid custom arch wire comprises alternating sequence of straightsegments and bent segments; wherein each of said straight segments isdesignated to be inserted into the slot of a specific virtual bracketfrom said set of virtual brackets; (c) selecting a first virtual bracketfrom said set of virtual brackets; (d) inserting the first straightsegment of said target custom arch wire into the slot of said firstvirtual bracket; wherein said first straight segment is designated forinsertion into the slot of said first virtual bracket; (e) selecting asecond virtual bracket from said set of virtual brackets; wherein saidsecond virtual bracket is the neighbor of said first virtual bracket;(f) inserting the second straight segment of said target custom archwire into the slot of said second virtual bracket; wherein said secondstraight segment is designated for insertion into the slot of saidsecond virtual bracket; (g) calculating deformation of said secondstraight segment; (h) evaluating the quality of insertion of said secondstraight segment into the slot of said second virtual bracket; and (i)optimizing said target custom arch wire if a collision is detected atsaid second virtual bracket, where by a portion of a bent segment getsinserted into the slot of said second virtual bracket.
 2. The method ofclaim 1, wherein said jaw is the upper jaw of said patient.
 3. Themethod of claim 1, wherein said jaw is the lower jaw of said patient. 4.The method of claim 1, wherein step (d) further comprises ligature tyingsaid first straight segment into the slot of said first virtual bracket.5. The method of claim 1, wherein in step (f), an incremental measuredforce is iteratively applied to said second straight segment whileinserting said second straight segment into the slot of said secondvirtual bracket.
 6. The method of claim 1, wherein said step ofoptimizing said target custom arch wire comprises modifying the lengthof said second straight segment, thereby modifying the design of saidtarget arch wire, so as to attempt to remove said collision at saidsecond virtual bracket.
 7. The method of claim 1, wherein the geometryof said target custom arch wire is non-planar in three-dimensions. 8.The method of claim 1,wherein said initial state comprises the patient'sdentition in malocclusion.
 9. The method of claim 1, wherein saidinitial state comprises the patient's dentition in an intermediate stateduring the course of the treatment.
 10. The method of claim 1, furthercomprising step (j) of displaying said target custom arch wire and saidvirtual brackets to a user.
 11. The method of claim 1, wherein saiddeformation in step (g) is expressed in terms of moment decomposed intothree parts: a torsional moment and two bending moments.
 12. The methodof claim 1, wherein said deformation in step (g) is expressed usingthree angles representing moment of cross section of said target customarch wire.